CN103701019A - 1[mu]m dissipative soliton mode-locked laser - Google Patents

Abstract

The present invention provides a 1 μm dissipative soliton mode-locked laser, which relates to the field of laser technology and solves the problem that existing devices are realized by spatial coupling. The coupling efficiency of the system is relatively low, the spatial coupling equipment is bulky, and the system stability is poor, which is not convenient for practical application. The problem. The present invention includes a wavelength division multiplexer, a gain fiber, an isolator and a coupling output element, wherein it also includes a bandpass filter, a first polarization controller and a second polarization controller, a wavelength division multiplexer, a gain fiber, a band The pass filter, the first polarization controller, the isolator, the second polarization controller and the coupling output element are sequentially connected by fibers to form an all-fiber ring cavity, and the length of the gain fiber is the length to make it vibrate at four energy levels. The invention not only can be used as a high-power ytterbium-doped laser pump source with high brightness and high beam quality, but also can further improve the output power of the ytterbium-doped fiber laser, and has the potential of being applied to cold amplification.

Description

1μm Dissipative Soliton Mode-locked Laser

technical field

The invention relates to the field of laser technology, in particular to a 1 μm dissipative soliton mode-locked laser. the

Background technique

Mode-locked fiber lasers are widely used in optical communications, micromachining, and photoelectric detection systems due to their excellent characteristics such as compact structure, low cost, good heat dissipation, and high output beam quality. With the continuous development and progress of fiber optic technology and mode-locking technology, the performance and some parameters of fiber laser output ultrashort pulses have reached or even exceeded that of traditional solid-state femtosecond lasers, and it is expected to become a popular ideal light source for ultrafast laser applications. the

Among the many mode-locked fiber lasers, the mode-locked fiber laser with Yb-doped fiber as the gain medium develops most rapidly. The spectral characteristics of ytterbium-doped fiber are mainly determined by ytterbium ions and matrix. Ytterbium-doped fiber based on phosphate, that is, ytterbium-doped phosphate fiber, has a wide absorption spectrum from 850nm to 1050nm and a wide emission spectrum from 900nm to 1100nm, so there is no absorption and concentration of excited states in Yb-doped phosphate fiber lasers. Quenching and multi-phonon transitions and other de-excitation processes can be pumped by a variety of pump sources, and are conducive to the realization of a wide range of wavelength tunable and ultrashort pulse output. The current high-power fiber lasers are mainly four-level ytterbium-doped fiber lasers in the 1μm band, which is determined by the energy level structure of ytterbium ions. The laser in the 1μm band can be used as a pump source for high-power erbium-doped and erbium-doped lasers with high brightness and high beam quality, which can further increase the output power of erbium-doped and erbium-doped fiber lasers, and is also conducive to expanding the source range of erbium-doped fiber lasers. And it is enlightening for the research and preparation of special wavelength optical fibers. In addition, 1 μm fiber laser has the potential to be applied to cold amplification. the

At present, there are few researches and reports on 1 μm ytterbium-doped mode-locked fiber laser at home and abroad. In 2003, O.G.Okhotnikov of the Tampere University of Technology in Finland used SESAM as a mode-locking element. The light was focused on the SESAM through a collimating focusing system, and a pair of gratings were inserted into the cavity to introduce negative dispersion to balance the positive dispersion in the cavity. By optimizing the inter-band energy and reflection characteristics of the multi-quantum well effect semiconductor saturable absorber, a mode-locked fiber laser with a tuning range of 980nm-1070nm, an output power of 3mW, and a pulse width of 1.6ps-2ps was obtained. The ytterbium-doped mode-locked laser is realized by spatial coupling, the coupling efficiency of the system is relatively low, the spatial coupling equipment is bulky, and the system stability is poor, which is not convenient for practical application. the

Therefore, a technical problem that needs to be solved urgently is: how to innovatively propose an effective measure to meet the needs of practical applications. the

Contents of the invention

In view of the deficiencies in the above problems, the present invention provides a 1 μm dissipative soliton mode-locked laser, which can not only be used as a pump source for high-power erbium-doped and ytterbium-doped lasers with high brightness and high beam quality, but also Further improve the output power of ytterbium-doped and erbium-doped fiber lasers, and it also has the potential to be applied to cold amplification. the

In order to solve the above problems, the present invention provides a 1 μm dissipative soliton mode-locked laser, which includes a wavelength division multiplexer, a gain fiber, an isolator and a coupling output element, and is characterized in that it also includes a band-pass filter, a first polarization control and the second polarization controller, the wavelength division multiplexer, the gain fiber, the bandpass filter, the first polarization controller, the isolator, the second polarization controller and the The coupling output elements are connected in order by optical fibers to form an all-fiber ring cavity. The length of the gain fiber is such that it can start oscillation at four energy levels. Through the suppression of the pulse output spectrum by the band-pass filter, the center wavelength can be achieved at 1μm laser output. the

Preferably, the band-pass filter is a band-pass filter with a center wavelength of 980nm, and its two ends are respectively connected to the wavelength division multiplexer and the first polarization controller by welding, and the band-pass filter The device provides additional amplitude modulation for the 980nm light beam, cuts the pulse sideband that is broadened into a chirped wide pulse in the total positive dispersion cavity, and narrows the pulse; the dissipated soliton pulse is generated by the band-pass filter. the

Preferably, both the first polarization controller and the second polarization controller are embedded polarization controllers, by adjusting the pressure and deflection angle of the first polarization controller and the second polarization controller to Implement model locking. the

Preferably, the gain fiber is an ytterbium-doped fiber, which is connected to the wavelength division multiplexer by fusion splicing. Ytterbium-doped fiber as the host. the

Preferably, the coupling output element is a polarization beam splitter, the two ends of which are respectively connected to the second polarization controller and the wavelength division multiplexer; the splitting ratio of the polarization beam splitter is 3:7, After the beam is split by the polarization beam splitter, 30% of the signal light is coupled out, and 70% of the signal light is retained for further transmission. the

Preferably, it also includes a pumping light source, the output end of the pumping light source is connected to the input end of the wavelength division multiplexer, and the wavelength division multiplexer is adjusted to increase the optical power output by the pumping beam. The light source is a 915nm semiconductor laser. the

Preferably, the number of the pump light sources is the same as the number of the wavelength division multiplexers. the

Preferably, the pump light source includes a first pump light source and a second pump light source, the wavelength division multiplexer includes a first wavelength division multiplexer and a second wavelength division multiplexer, and the first pump The output end of the pumping light source is connected to the input end of the first wavelength division multiplexer, and the output end of the second pumping light source is connected to the input end of the second wavelength division multiplexer. the

Preferably, the first wavelength division multiplexer and the second wavelength division multiplexer are respectively arranged at both ends of the gain fiber, and are respectively connected to the gain fiber by fusion splicing. the

Compared with prior art, the present invention has the following advantages:

The present invention realizes the all-fiber structure through the optical fiber fusion process, uses a 915nm single-mode semiconductor laser as the pumping source, adopts a double-ended pumping method, realizes mode-locking in a nonlinear polarization rotation mode-locking mode, and inserts a passband range of 960- The band-pass filter of 990 limits the range of the output spectrum and achieves stable mode-locking. The mode-locking repetition frequency is 17.786MHz, the maximum output power is 30mW, and the center wavelength of the output spectrum is 1000nm; The pump source with high beam quality can further increase the output power of Ytterbium-doped and Erbium-doped fiber lasers, and it also has the potential to be applied to cold amplification. the

Description of drawings

Fig. 1 is the structural representation of the first embodiment of the present invention;

Fig. 2 is a schematic structural diagram of the second embodiment of the present invention. the

The main component symbols are explained as follows:

1-First pumping light source 2-Second pumping light source

3-First WDM 4-Second WDM

5-gain fiber 6-bandpass filter

7-First polarization controller 8-Second polarization controller

9-isolator 10-polarization beam splitter

11-pump light source 12-wavelength division multiplexer

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and examples. However, the examples given are not intended to limit the present invention. the

As shown in Figure 1, this embodiment includes a wavelength division multiplexer, a gain fiber 5, an isolator 9, and a coupling output element, wherein a bandpass filter 6, a first polarization controller 7, and a second polarization controller are also included 8. Wavelength division multiplexer, gain fiber 5, bandpass filter 6, first polarization controller 7, isolator 9, second polarization controller 8 and coupling output elements are connected in sequence with optical fibers to form an all-fiber ring cavity, and the gain The length of the fiber is such that it starts to vibrate at four energy levels. the

In the gain fiber, there is a problem of gain competition between three and four energy levels. By choosing the length of the gain fiber reasonably, only four energy levels start to oscillate, and the 1030nm of the four energy levels corresponds to an emission peak of ytterbium ions, and its The absorption cross section is very small, which makes it easy to vibrate when the threshold of 1030nm is low. However, since the center wavelength range of the 6 bands of the bandpass filter is between 960-990nm, it has a limiting effect on the pulse output spectrum, and the 1030nm light is not in the bandpass filter. 6 is suppressed within the pass-band range of the band-pass filter 6, so that the stimulated emission cross-section is relatively large and the light in the 1 μm band within the pass-band range of the band-pass filter 6 oscillates, thus realizing the laser output with a center wavelength of 1 μm. the

The all-fiber ring cavity has a compact structure, better stability than the space coupling method, and has lower laser threshold and loss. the

The maximum output power of the pump light source is 250mW, and it is pumped in a double-ended pumping mode. The pump light is coupled into the ring cavity through a wavelength division multiplexer with filtering function, and the single-mode 915nm semiconductor laser with pigtail passes through The way of welding is connected with the wavelength division multiplexer of 915/980. The present invention can also adopt a single-end pumping method, but compared with a double-ended pumping method, the output power will be greatly reduced. The wavelength division multiplexer with filtering function is used as a coupling system for the pump light and because of its special structure, it protects the pump and prevents the feedback light from damaging the pump. the

The gain fiber has a high absorption coefficient for 915nm pump light, and the absorption coefficient is 589dB/m. the

The band-pass filter is one of the key devices to achieve 1μm dissipative soliton mode-locking, its two ends are respectively connected to the wavelength division multiplexer and isolator 9, and the band-pass filter 6 with a center wavelength of 980nm can provide additional amplitude The modulation effect cuts the pulse sidebands that are broadened into chirped wide pulses in the fully positive dispersion cavity, narrows the pulse, and plays an important role in stable mode locking and pulse shaping. is a dissipative effect, so it is also the cause of the dissipative soliton pulse. the

The polarization controller and isolator 9 are the core components of polarization rotation mode-locking. The isolator determines the direction of light transmission in the all-fiber ring cavity and ensures the unidirectional transmission of light in the cavity; while the embedded polarization controller adjusts the first The pressure and deflection angle of the polarization controller 7 and the second polarization controller 8 implement mode locking. the

The four-level 1μm dissipative soliton mode-locked laser is realized by using the polarization rotation mode-locking method. The pump light is coupled into the ring cavity, and the polarization state of the light is changed into linear polarization through the isolator. By adjusting the pressure of the polarization controller and The rotation angle changes linearly polarized light into elliptically polarized light. The transmission of polarized light in the cavity is affected by nonlinear effects. Since the nonlinear effect is related to the light intensity, the polarization states of different parts of the entire pulse are rotated differently. Adjust the polarization controller , so that the high-intensity part of the pulse center passes through the isolator, while the weaker flanks are suppressed, so as to realize the narrowing of the pulse, realize stable mode-locking with the assistance of the band-pass filter, and finally couple the output through the polarization beam splitter 10 . the

Ytterbium-doped phosphate optical fiber is a phosphate-based optical fiber, which has high solubility for ytterbium ions, long fluorescence lifetime, small nonlinearity and large photodarkening threshold, and can obtain a high concentration of Doping, so that it has a high absorption coefficient for the 915nm pump light, high power output can be achieved with a very short fiber, and it is also beneficial to suppress the four-level vibration, and obtain a three-level 980nm laser. The same effect can be achieved by replacing ytterbium-doped phosphate fiber with ytterbium-doped fiber with high doping concentration and quartz-based matrix or with ordinary ytterbium-doped fiber with high doping concentration. the

This embodiment includes two 915nm semiconductor lasers with a maximum power of 250mW, namely the first semiconductor laser and the second semiconductor laser, and two 915/980 wavelength division multiplexers with filtering functions, namely the first wavelength division multiplexer 3 and the second wavelength division multiplexer 4, the absorption coefficient of 915nm light is 589dB/m, the 8.8cm-long ytterbium-doped phosphate fiber, the bandpass filter with a passband range of 960nm-990nm 6, two embedded polarization controllers , that is, the first polarization controller 7 and the second polarization controller 8, the isolator 9 of 2W, and the polarization beam splitter 10 with a coupling ratio of 30:70. In addition to the embedded first polarization controller 7 and the second polarization controller 8, other components are connected together by fusion to form an all-fiber ring cavity, and then the two embedded first polarization controllers 7 and the second polarization controller The two polarization controllers 8 are respectively installed on the optical fibers next to the two sides of the isolator 9 . The direction of the intracavity laser is determined by the isolator 9. The 915nm pump light is coupled into the ring cavity through the 915/980 FWDM, and the light passes through the bandpass filter 6, the first polarization controller 7, the isolator 9, The second polarization controller 8, the polarization beam splitter 10 of 30:70, adjust the first polarization controller 7 and the second polarization controller 8, make the output optical power maximum, then adjust the first polarization controller 7 and the second polarization The controller 8 implements mode locking. Stable continuous mode-locking appears on the observation oscilloscope, the mode-locking repetition frequency is 17.786MHz, the maximum output power is 30mW when the pump power is 240mW, and the central wavelength of the output spectrum is 1000nm, the typical characteristics of the dissipative soliton mode-locking spectrum appear, and there are steep peaks at both ends of the spectrum. The edges and peaks appear at both ends. the

As shown in Figure 2, a 915nm semiconductor laser with a maximum power of 250mW is included in this embodiment, a 915/980 wavelength division multiplexer 12 with a filtering effect, a 915nm light absorption coefficient of 589dB/m, and a doped laser with a length of 8.8cm Ytterbium phosphate fiber, bandpass filter 6 with a passband range of 960nm-990nm, two embedded polarization controllers, namely the first polarization controller 7 and the second polarization controller 8, 2W isolator 9, coupling ratio 30 :70 polarizing beam splitter 10. In addition to the embedded first polarization controller 7 and the second polarization controller 8, other components are connected together by fusion to form an all-fiber ring cavity, and then the two embedded first polarization controllers 7 and the second polarization controller The two polarization controllers 8 are respectively installed on the optical fibers next to the two sides of the isolator 9 . The direction of the intracavity laser is determined by the isolator 9, and the 915nm pump light is coupled into the ring cavity through the 915/980 FWDM, and the light passes through the bandpass filter 6, the first polarization controller 7, the isolator 9, The second polarization controller 8, the polarization beam splitter 10 of 30:70, adjust the first polarization controller 7 and the second polarization controller 8, make the output optical power maximum, then adjust the first polarization controller 7 and the second polarization The controller 8 implements mode locking. Observe that stable continuous mode-locking appears on the oscilloscope, the central wavelength of the output spectrum is 1000nm, and the typical characteristics of the dissipative soliton mode-locked spectrum appear, with steep edges and sharp peaks at both ends of the spectrum. the

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. the

Claims (9)

1. A 1 μm dissipative soliton mode-locked laser, comprising a wavelength division multiplexer, a gain fiber, an isolator and a coupling output element, characterized in that it also includes a bandpass filter, a first polarization controller and a second polarization control device, the wavelength division multiplexer, the gain fiber, the bandpass filter, the first polarization controller, the isolator, the second polarization controller and the coupling output element Sequentially connected to form an all-fiber ring cavity, the length of the gain fiber is to make it vibrate at four energy levels, through the suppression of the pulse output spectrum by the band-pass filter, the laser output with a center wavelength of 1 μm is realized. 2. The 1 μm dissipative soliton mode-locked laser according to claim 1, wherein the band-pass filter is a band-pass filter with a center wavelength of 980nm, and its two ends are respectively connected to the wavelength division The multiplexer is connected to the first polarization controller, and the bandpass filter provides additional amplitude modulation for the 980nm light beam, cuts the pulse sidebands that are broadened into chirped wide pulses in the full positive dispersion cavity, and narrows the pulse ; Dissipative soliton pulses are produced by the bandpass filter. 3. The 1 μm dissipative soliton mode-locked laser according to claim 2, wherein both the first polarization controller and the second polarization controller are embedded polarization controllers, and by adjusting the first The pressure and deflection angle of a polarization controller and the second polarization controller are used to achieve mode locking. 4. The 1 μm dissipative soliton mode-locked laser according to claim 3, wherein the gain fiber is an ytterbium-doped fiber, which is connected to the wavelength division multiplexer by fusion splicing, and the ytterbium-doped fiber is selected from Highly doped ordinary ytterbium-doped fiber, ytterbium-doped phosphate fiber, or ytterbium-doped fiber based on silica. 5. The 1 μm dissipative soliton mode-locked laser according to claim 4, wherein the coupling output element is a polarization beam splitter, and its two ends are respectively connected to the second polarization controller and the wavelength division multiplexer connected with a device; the splitting ratio of the polarizing beam splitter is 3:7, after the beam is split by the polarizing beam splitter, 30% of the signal light is coupled out, and 70% of the signal light is retained for further transmission. 6. The 1 μm dissipative soliton mode-locked laser according to any one of claims 1 to 5, further comprising a pumping light source, the output of the pumping light source is connected to the input of the wavelength division multiplexer The terminals are connected, and the wavelength division multiplexer is adjusted to increase the optical power output by the pumping beam, and the pumping light source is a 915nm semiconductor laser. 7. The 1 μm dissipative soliton mode-locked laser according to claim 6, wherein the number of the pump light sources is the same as the number of the wavelength division multiplexers. 8. The 1 μm dissipative soliton mode-locked laser according to claim 7, wherein the pump light source includes a first pump light source and a second pump light source, and the wavelength division multiplexer includes a first wave The division multiplexer and the second wavelength division multiplexer, the output end of the first pumping light source is connected to the input end of the first wavelength division multiplexer, the output end of the second pumping light source is connected to the The input terminal of the second wavelength division multiplexer is connected. 9. The 1 μm dissipative soliton mode-locked laser according to claim 8, wherein the first wavelength division multiplexer and the second wavelength division multiplexer are respectively arranged at both ends of the gain fiber , and are respectively connected to the gain fibers by fusion splicing.

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